Suspension bridge and method of erecting same

Abstract

A suspension bridge has a pair of horizontally spaced towers between which is spanned a main catenary cable. A flexible spacer element, normally a cable, extends along the main cable between the towers and is provided with generally equispaced spacers. Respective hanger assemblies are fixed at the spacers and can slide on the main cable between the towers. Respective upright hangers defining a vertical plane with the main cable have upper ends connected to the hanger assemblies and lower ends and are provided with adjusters between these ends for shortening and lengthening the distance therebetween. Respective girders are secured to the lower ends and extend generally perpendicular to the plane and respective path sections extend generally horizontally and each have one end hooked over a respective one of the girders and another end hooked over an adjacent girder. The sections each have an effective length between the respective girders equal generally to the distance between adjacent spacers of the spacer element and they together form a continuous path between the towers.

We claim: 
     
       1. A suspension bridge comprising: a pair of horizontally spaced towers;   a main catenary cable suspended from and extending between said towers;   a flexible spacer element extending along said main cable between said towers and provided with generally equispaced spacers;   respective hanger assemblies fixed at said spacers and slidable on said main cable between said towers;   respective upright hangers defining a vertical plane with said main cable and having upper ends connected to the respective hanger assemblies and lower ends;   respective means between said ends for shortening and lengthening the distance therebetween;   respective girders secured to said lower ends and extending generally perpendicular to said plane; and   respective path sections extending generally horizontally and each having one end hooked over a respective one of said girders and another end hooked over an adjacent girder, said sections each having an effective length between the respective girders equal generally to the distance between adjacent spacers of said spacer element, said sections together forming a continuous path between said towers, said path section having ends formed with downwardly open recesses receiving the respective girders and linking each path section at each of its ends to the respective girder for pivoting relative thereto generally about the axis of the respective girder, said bridge further comprising means for securing the path-section ends down on the respective girders.   
     
     
       2. The suspension bridge defined in claim 1 wherein said towers each have a plurality of legs formed of longitudinally interfitted separable leg sections and a holder for the respective end of said main cable. 
     
     
       3. The suspension bridge defined in claim 2 wherein said leg sections are made of a light metal and are provided with interfittable ends. 
     
     
       4. The suspension bridge defined in claim 3 wherein each of said supports has at least three such legs and a cap at the upper ends thereof and provided with a pulley arrangement constituting the respective holder. 
     
     
       5. The suspension bridge defined in claim 3 wherein said legs have lower ends provided with horizontal disks by means of which they bear on the ground. 
     
     
       6. The suspension bridge defined in claim 3 wherein said legs have lower ends and said towers each comprise a closed loop of cable connected to the respective lower leg ends. 
     
     
       7. The suspension bridge defined in claim 1 wherein said girders are formed as generally cylindrical tubes and said means for securing includes respective cables attached underneath said tubes to path-section ends of adjacent path sections. 
     
     
       8. The suspension bridge defined in claim 7 wherein said hangers include suspender cables looped through said girders at the ends thereof. 
     
     
       9. The suspension bridge defined in claim 8 wherein said girders carry respective profiled support rails over which said recesses fit and to which the securing means secure said path-section ends. 
     
     
       10. The suspension bridge defined in claim 9 wherein said securing means includes respective pairs of holder plates longitudinally slidable along said rails and bolts securing each pair of holder plates to the sides of adjacent path-section ends. 
     
     
       11. The suspension bridge defined in claim 1 wherein said path sections each include two parallel box-beam longitudinal members and transverse members bridging same. 
     
     
       12. The suspension bridge defined in claim 1 wherein each hanger assembly includes three parts forming an upper passage for said main cable, a lower passage for said spacer element, and a transverse rod securing said parts together and securing a respective upper end of a hanger to them. 
     
     
       13. The suspension bridge defined in claim 12 wherein said spacer element is a cable and said spacers are sleeves fixed thereon, said parts forming a seat for the respective spacer. 
     
     
       14. A method of building a suspension bridge including: a pair of horizontally spaced towers;   a main catenary cable suspended from and extending between said towers;   a flexible spacer element extending along said main cable between said towers and provided with generally equispaced spacers;   respective hanger assemblies fixed at said spacers and slidable on said main cable between said towers;   respective upright hangers defining a vertical plane with said main cable and having upper ends connected to the respective hanger assemblies and lower ends;   respective mechanisms between said ends for shortening and lengthening the distance therebetween;   respective girders secured to said lower ends and entending generally perpendicular to said plane; and   respective path sections extending generally horizontally and each having one end hooked over a respective one of said girders and another end hooked over an adjacent girder, said sections each having an effective length between the respective girders equal generally to the distance between adjacent spacers of said spacer element, said sections together forming a continuous path between said towers, said method comprising the steps sequentially: (a) erecting said towers;   (b) drawing said main cable between the erected towers;   (c) slidably fitting at one of the towers a hanger assembly to the spanned main cable and securing it to a respective one of said spacers of said spacer element and securing a hanger to this hanger assembly and a girder to this hanger to form a hanger unit slidable along the main cable and attached to said respective one spacer;   (d) pivotally coupling one end of a path section to the girder of the hanger unit of step (c) at the one tower;   (e) pulling said spacer unit from one tower toward the other tower thereby drawing the one spacer with the respective hanger unit attached to it from said one tower toward the other tower through a distance along said main cable equal generally to said distance between adjacent spacers on said spacer element;   (f) repeating step (c) with the next spacer along said spacer element and pivotally coupling the other end of the path section of step (d) and one end of yet another path section to the girder of the thus formed hanger unit, all still at the one tower;   (g) repeating steps (d), (e), and (f) with successive hanger assemblies, hangers, girders, and roadway sections to form of the sections a continuous path extending between said towers; and   (h) adjusting the distance between the upper and lower end of said hangers by means of said mechanisms to straighten said path.